Certain embodiments of the present technology relate to wireless devices. More specifically, certain embodiments of the present technology relate to wireless earphone systems used in connection with devices that can output an audio signal.
The use of wireless speakers and earphones is well known. There are, however, several disadvantages associated with existing wireless earphone systems. For example, existing wireless earphones do not sufficiently exclude external noise. As a result, in order for an earphone user to enjoy music and/or understand speech, the earphone user increases the earphone volume to uncomfortable and/or unsafe levels. This issue can be exacerbated, for example, when an earphone user is on a train, in an automobile, on an airplane, using the subway, and/or on a busy street.
Another example of a disadvantage associated with existing wireless earphones is that they provide relatively poor sound quality and fidelity. The noise level of existing wireless earphones is almost always higher than that of the MP3 player or other audio source itself. Also, existing wireless earphones have 25-band Accuracy Scores of about 30-79%, whereas wired earphones that listeners rate as true high-fidelity have 25-band Accuracy Scores of 80% and greater.
Another example of a disadvantage associated with existing wireless earphones is that they are relatively bulky and heavy. As a result, a headband and/or other support means is used to secure the earphones near the ears, thereby reducing earphone user comfort and making earphones less convenient to wear and/or carry.
Many factors contribute to earphone size and weight. Such factors include circuitry size, battery size, and antenna size. While circuits and batteries continue to become smaller and more lightweight, antennas require unique consideration. For example, a quarter-wave antenna operating at 2.4 GHz requires about 31.25 mm of effective length when it is free from nearby conductors and operates above a real or virtual ground plane. In practice, such a condition arises when the antenna extends from a circuit board, which acts as a ground plane, such that the antenna is substantially perpendicular to the plane created by the surface of the circuit board. Even shorter antennas can sometimes be used with special methods, but all require 25-32 mm of relatively free space inside the earphone housing. The required free space inside the earphone housing contributes substantially to the total volume of the earphone. In such applications, disposing an antenna in an earphone housing can increase the size of the earphone housing by a factor of about 25 mm times the surface area of the housing, resulting in a device that is substantially larger than it would be without the antenna.
In other applications, a quarter-wave antenna can be placed above and substantially parallel to the ground plane formed by the circuit board. In general, the antenna is placed a distance of at least 6 mm from the ground plane (and often 10 mm from the ground plane) in order to avoid antenna efficiency losses.
In other applications, the antenna may be arranged to stick out of the earphone housing in whole or in part (for example, as is the case with many cell phones). However, it is sometimes undesirable to have the antenna stick out of the earphone housing, and such applications can result in a device that is substantially larger than it would be without the antenna.
The most promising recent wireless technology has been Bluetooth, an industrial specification for wireless personal area networks. The early Bluetooth circuits were large and required large battery currents. However, more recent Bluetooth circuits are smaller and exhibit reduced power drain. Further, battery energy storage density continues to improve.
Such improvements have resulted in further development of wireless earphones. For example, Teling Technology Company, has announced a wireless cellular phone headset, the BTH-11, that does not require a headband and/or other support means, and appears to be supported only by the ear. However, the BTH-11 headset is for a low-quality monaural telephone audio signal rather than a high-fidelity stereophonic signal. Such a headset would not include the amount of circuitry found in a stereophonic headset, which, for example, requires a higher signal to noise ratio and processes more data. Further, battery consumption would be as little as half that of a stereophonic headset. Nonetheless, the BTH-11 headset is relatively bulky. It has listed dimensions of 75.2 mm×17 mm×33 mm, resulting in a volume of 42,187 cubic mm, and appears to require parking in a belt-holder to recharge the battery in the headset. Further, while the ear tips shown in connection with the BTH-11 headset appear adequate for monaural telephonic reproduction, they would not have the stability or sealing properties required for true high-fidelity stereophonic reproduction, for example, because they do not appear to have a length, width or design that would allow them to substantially acoustically seal an ear canal.
Further limitations and disadvantages of conventional and traditional approaches will become apparent to one of skill in the art, through comparison of such systems with some aspects of the present technology as set forth in the remainder of the present application with reference to the drawings. There is, therefore, a need for wireless earphone systems that provide improved external noise exclusion, improved sound quality and fidelity, and/or reduced size and weight.